Proximity service channel allocation based on random access channel procedure

ABSTRACT

Systems, methods, apparatuses, and computer program products for a random access channel (RACH) procedure based proximity-based service channel allocation are provided. One method includes controlling receiving, by a network node, a request for proximity-based service on a random access channel, the request being for at least one resource, and determining whether the requested at least one resource is allocable within a random access contention window. When the at least one resource is allocable, the method may include preparing a transmission of allocation information on a common control channel. When the at least one resource is not allocable, the method may include preparing a response for the request on the random access response channel, and preparing a transmission of allocation information either on common control channel or dedicated control channel.

BACKGROUND

Field

Certain embodiments generally relate to communication systems, and forexample, to device-to-device (D2D) communication integrated into acommunications network, such as long-term evolution (LTE) or long-termevolution advanced (LTE-A) cellular network specified by the 3rdGeneration Partnership Project (3GPP).

Description of the Related Art

Two types of communication networks include cellular networks and ad-hocnetworks. A cellular network is a radio network made up of one or morecells, where each cell is served by at least one centralized controller,such as a base station (BS), a Node B, or an evolved Node B (eNB). In acellular network, a user equipment (UE) communicates with another UE viathe centralized controller, where the centralized controller relaysmessages sent by a first UE to a second UE, and visa-versa. In contrast,in an ad-hoc network, a UE directly communicates with another UE,without the need of a centralized controller. Utilizing a cellularnetwork versus an ad-hoc network has its benefits and drawbacks. Forexample, utilizing a cellular network over an ad-hoc network providesthe benefit of easy physical resource control and interference control.However, utilizing a cellular network over an ad-hoc network alsoprovides the drawback of inefficient physical resource utilization. Forinstance, additional physical resources may be required in a cellularnetwork when the two UEs are close to each other, as compared to anad-hoc network.

A hybrid network utilizes both a cellular mode and a device-to-device(D2D) transmission mode. In a hybrid network, a UE may choose tocommunicate either via a cellular mode or a D2D transmission mode. As anexample, a hybrid network may allow UEs to communicate either via acellular mode (i.e. via a centralized controller) or via a D2Dtransmission mode where the UEs may establish a direct channel which mayor may not be under the control of a centralized controller. The UEand/or its controlling network may make this selection depending onwhich mode provides better overall performance. Thus, a hybrid networkmay improve total system performance over a cellular network or anad-hoc network. However, in order to utilize a hybrid network, issuesrelated to physical resource sharing and interference situations mayneed to be addressed.

In addition, proximity services (ProSe)/D2D discovery and communicationis one of the ongoing study items for 3GPP Release 12 (Rel-12)standardization (as well as Release 13 and beyond). D2D scenarios thatare currently being studied in 3GPP include D2D in network coverage, outof network coverage, and partial network coverage scenarios. Forexample, Public Safety (PS) 1-to-Multiple (1:M) D2D group communicationin both out-of-coverage and in-coverage scenarios are a particular focusdue to the potential public safety applications.

SUMMARY

One embodiment is directed to a method including controlling receiving,by a network node, a request for proximity-based service on a randomaccess channel, the request being for at least one resource, anddetermining whether the requested at least one resource is allocablewithin a random access contention window. When the at least one resourceis allocable, the method may further include preparing a transmission ofallocation information on a common control channel. When the at leastone resource is not allocable, the method may further include preparinga response for the request on the random access response channel, andpreparing a transmission of allocation information either on commoncontrol channel or dedicated control channel.

Another embodiment is directed to an apparatus including at least oneprocessor and at least one memory including computer program code. Theat least one memory and the computer program code are configured, withthe at least one processor, to cause the apparatus at least to controlreceiving a request for proximity-based service on a random accesschannel, the request being for at least one resource, and to determinewhether the requested at least one resource is allocable within a randomaccess contention window. When the at least one resource is allocable,the apparatus may be caused to prepare a transmission of allocationinformation on a common control channel. When the at least one resourceis not allocable, the apparatus may be caused to prepare a response forthe request on the random access response channel, and prepare atransmission of allocation information either on common control channelor dedicated control channel.

Another embodiment is directed to a computer program embodied on acomputer readable medium. The computer program may be configured tocontrol a processor to perform a method including controlling receiving,by a network node, a request for proximity-based service on a randomaccess channel, the request being for at least one resource, anddetermining whether the requested at least one resource is allocablewithin a random access contention window. When the at least one resourceis allocable, the method may further include preparing a transmission ofallocation information on a common control channel. When the at leastone resource is not allocable, the method may further include preparinga response for the request on the random access response channel, andpreparing a transmission of allocation information either on commoncontrol channel or dedicated control channel.

Another embodiment is directed to an apparatus including means forcontrolling receiving a request for proximity-based service on a randomaccess channel, the request being for at least one resource, and meansfor determining whether the requested at least one resource is allocablewithin a random access contention window. When the at least one resourceis allocable, the apparatus may further include means for preparing atransmission of allocation information on a common control channel. Whenthe at least one resource is not allocable, the apparatus may furtherinclude means for preparing a response for the request on the randomaccess response channel, and means for preparing a transmission ofallocation information either on common control channel or dedicatedcontrol channel.

Another embodiment is directed to a method including determining, by adevice, a need for at least one resource for proximity-based service,controlling transmission of a resource request on a random accesschannel for the at least one resource, and monitoring feedback inresponse to the resource request. When resource allocation for theproximity-based service is obtained on a common control channel, themethod may further include maintaining a current activity status. When aresponse to the resource request is obtained on a random access responsechannel, the method may further include remaining in a connected statefor obtaining resource allocation for the proximity-based service. Whena response to the resource request is not obtained, the method mayfurther include controlling retransmission of the resource request on arandom access channel after a back-off period of time.

Another embodiment is directed to an apparatus including at least oneprocessor and at least one memory including computer program code. Theat least one memory and the computer program code are configured, withthe at least one processor, to cause the apparatus at least to determinea need for at least one resource for proximity-based service, controltransmission of a resource request on a random access channel for the atleast one resource, and monitor feedback in response to the resourcerequest. When resource allocation for the proximity-based service isobtained on a common control channel, the apparatus may be caused tomaintain a current activity status. When a response to the resourcerequest is obtained on a random access response channel, the apparatusmay be caused to remain in a connected state for obtaining resourceallocation for the proximity-based service. When a response to theresource request is not obtained, the apparatus may be caused to controlretransmission of the resource request on a random access channel aftera back-off period of time.

Another embodiment is directed to a computer program embodied on acomputer readable medium. The computer program may be configured tocontrol a processor to perform a method including determining, by adevice, a need for at least one resource for proximity-based service,controlling transmission of a resource request on a random accesschannel for the at least one resource, and monitoring feedback inresponse to the resource request. When resource allocation for theproximity-based service is obtained on a common control channel, themethod may further include maintaining a current activity status. When aresponse to the resource request is obtained on a random access responsechannel, the method may further include remaining in a connected statefor obtaining resource allocation for the proximity-based service. Whena response to the resource request is not obtained, the method mayfurther include controlling retransmission of the resource request on arandom access channel after a back-off period of time.

Another embodiment is directed to an apparatus including means fordetermining a need for at least one resource for proximity-basedservice, means for controlling transmission of a resource request on arandom access channel for the at least one resource, and means formonitoring feedback in response to the resource request. When resourceallocation for the proximity-based service is obtained on a commoncontrol channel, the apparatus may further include means for maintaininga current activity status. When a response to the resource request isobtained on a random access response channel, the apparatus may furtherinclude means for remaining in a connected state for obtaining resourceallocation for the proximity-based service. When a response to theresource request is not obtained, the apparatus may further includemeans for controlling retransmission of the resource request on a randomaccess channel after a back-off period of time.

BRIEF DESCRIPTION OF THE DRAWINGS

For proper understanding of the invention, reference should be made tothe accompanying drawings, wherein:

FIG. 1 illustrates an example contention based random access procedure;

FIG. 2a illustrates a flow chart of a method according to oneembodiment;

FIG. 2b illustrates a flow chart of a method according to anotherembodiment;

FIG. 3 illustrates a signaling diagram depicting an embodiment of amethod for a random access procedure based D2D channel allocation;

FIG. 4a illustrates an apparatus according to one embodiment;

FIG. 4b illustrates an apparatus according to another embodiment;

FIG. 5a illustrates a block diagram of an apparatus according to anembodiment; and

FIG. 5b illustrates a block diagram of an apparatus according to anotherembodiment.

DETAILED DESCRIPTION

It will be readily understood that the components of the invention, asgenerally described and illustrated in the figures herein, may bearranged and designed in a wide variety of different configurations.Thus, the following detailed description of the embodiments of systems,methods, apparatuses, and computer program products for a random accesschannel (RACH) procedure based proximity-based service channelallocation, as represented in the attached figures, is not intended tolimit the scope of the invention, but is merely representative ofselected embodiments of the invention.

The features, structures, or characteristics of the invention describedthroughout this specification may be combined in any suitable manner inone or more embodiments. For example, the usage of the phrases “certainembodiments,” “some embodiments,” or other similar language, throughoutthis specification refers to the fact that a particular feature,structure, or characteristic described in connection with the embodimentmay be included in at least one embodiment of the present invention.

Thus, appearances of the phrases “in certain embodiments,” “in someembodiments,” “in other embodiments,” or other similar language,throughout this specification do not necessarily all refer to the samegroup of embodiments, and the described features, structures, orcharacteristics may be combined in any suitable manner in one or moreembodiments. Additionally, if desired, the different functions discussedbelow may be performed in a different order and/or concurrently witheach other. Furthermore, if desired, one or more of the describedfunctions may be optional or may be combined. As such, the followingdescription should be considered as merely illustrative of theprinciples, teachings and embodiments of this invention, and not inlimitation thereof.

Some embodiments of the invention are applicable to LTE-Advanced,including 3GPP LTE-A Rel-12, Rel-13 and beyond, which addressesLTE-Advanced support for network-controlled D2D discovery andcommunication without limitation to LTE-Advanced. The 3GPP has beguncarrying out a study for potential services and requirements for D2Dcommunications, referred to as Proximity Services (ProSe). One objectiveof this study is to look at use cases and identify potentialrequirements for an operator network controlled discovery andcommunications between devices that are in proximity, under continuousnetwork control, and/or are under 3GPP network coverage. This could befor the purposes of commercial/social use, network offloading, publicsafety, and/or integration of current infrastructure services to assurethe consistency of the user experience including reachability andmobility aspects.

The use of a star-topology D2D cluster in which a selected device istaking a special role in coordinating and perhaps controlling possibleD2D communications among cluster members is one of the approaches forsupporting ProSe D2D communications. An example of how a D2D cluster mayprovide the broadcast based D2D communications includes the cluster head(CH) coordinating and allocating physical channel resources for clustermembers to transmit for their requested individual user(s) or usergroup(s) within the cluster.

Network controlled D2D communication for in-network-coverage scenariohas been considered. However, it has only been considered for either theevolved Node B (eNB) to coordinate D2D clusters within the cell or theeNB to act as D2D cluster head (CH) with new set of functions andoperations of D2D CH. Reuse of current E-UTRAN functionalities tofacilitate D2D functions and operations has been considered too, inwhich it requires D2D UEs to be kept in radio resource control (RRC)connected state in order to get the control from E-UTRAN for D2Doperations. However, this will lead to waste of radio resource, highcomplexity and signaling overhead for establishing of RRC connection andmaintaining active user equipment (UE) context and mobility managementif D2D UEs have only D2D service without normal EPS service. Therefore,considering D2D UE requests resource allocation from eNB for D2Dcommunication, it may be preferable to reuse random access (RA)procedure for contention based D2D channel allocation request when inE-UTRAN coverage instead of introducing another kind of contention basedmechanism or establishing unnecessary RRC connection for the requestingUE. Therefore, embodiments of the present invention provide RA procedurebased D2D channel allocation for the eNB to coordinate the resourceallocation of D2D communication in in-coverage scenarios. In addition,it is noted that this approach may also be applied for out-of-coveragescenarios.

FIG. 1 illustrates an example contention based random access procedurein LTE. It should be appreciated, though, that FIG. 1 is presentedherein only as an example and should not be taken as limiting theinvention. For example, in future systems, random access messages maydiffer from those presented herein and user device activity statuses maynot be limited to connected or idle. The same applies to other examples,too. In the example of FIG. 1, the four steps of the contention basedrandom access procedures include: (1) Random Access Preamble on randomaccess channel (RACH) in uplink, (2) Random Access Response generated bymedium access control (MAC) on downlink shared channel (DL-SCH), (3)First scheduled uplink (UL) transmission on uplink shared channel(UL-SCH), and (4) Contention Resolution on downlink (DL).

For the Random Access Preamble on RACH in uplink (1), there are twopossible groups defined where one is optional. If both groups areconfigured the size of message 3 and the pathloss is used to determinewhich group a preamble is selected from, the group to which a preamblebelongs provides an indication of the size of the message 3 and theradio conditions at the UE. The preamble group information along withthe necessary thresholds are broadcast on system information.

The Random Access Response generated by MAC on DL-SCH (2) may have thefollowing characteristics: semi-synchronous (within a flexible window ofwhich the size is one or more TTI) with message (1), no hybrid automaticrepeat request (HARQ), addressed to Random Access Radio NetworkTemporary Identifier (RA-RNTI) on Physical Downlink Control Channel(PDCCH), conveys at least RA-preamble identifier, Timing Alignmentinformation for the primary timing advance group (pTAG), initial ULgrant and assignment of Temporary Cell Radio Network TemporaryIdentifier (C-RNTI) (which may or may not be made permanent uponcontention resolution), and intended for a variable number of UEs in oneDL-SCH message.

The first scheduled UL transmission on UL-SCH (3) may have the followingcharacteristics: uses HARQ, the size of the transport blocks depends onthe UL grant conveyed in message (2) and is at least 80 bits. Forinitial access, scheduled transmission (3) conveys the RRC ConnectionRequest generated by the RRC layer and transmitted via common controlchannel (CCCH) and at least non-access stratum (NAS) UE identifier butno NAS message, and radio link control (RLC) transparent mode (TM) hasno segmentation. For RRC Connection re-establishment procedure,scheduled transmission (3) conveys the RRC Connection re-establishmentrequest generated by the RRC layer and transmitted via CCCH, RLC TM hasno segmentation, and does not contain any NAS message. After handover,in the target cell, scheduled transmission (3) conveys the ciphered andintegrity protected RRC Handover Confirm generated by the RRC layer andtransmitted via dedicated control channel (DCCH), conveys the C-RNTI ofthe UE (which was allocated via the Handover Command), and includes anuplink Buffer Status Report when possible. For other events, scheduledtransmission (3) conveys at least the C-RNTI of the UE.

For contention resolution message (4), early contention resolution shallbe used, i.e., eNB does not wait for NAS reply before resolvingcontention. It is not synchronized with message 3 and HARQ is supported.It is addressed to: the Temporary C-RNTI on physical downlink controlchannel (PDCCH) for initial access and after radio link failure; and/orthe C-RNTI on PDCCH for UE in RRC CONNECTED. HARQ feedback istransmitted only by the UE which detects its own UE identity, asprovided in message (3), echoed in the contention resolution message(4). For initial access and RRC Connection re-establishment procedure,no segmentation is used in RLC layer, i.e. RLC transparent mode (RLC-TM)is used.

The Temporary C-RNTI is promoted to C-RNTI for a UE which detects RAsuccess and does not already have a C-RNTI; it is dropped by others. AUE which detects random access (RA) success and already has a C-RNTI,resumes using its C-RNTI.

Certain embodiments of the invention, considering eNB as D2D CH tocoordinate the channel allocation for D2D broadcast and groupcommunication for in-network-coverage scenario, provide a variation ofthe RA procedure in E-UTRAN for D2D UE to request D2D channel allocationfrom eNB without unnecessary RRC connection establishment.

In this embodiment, the eNB may act as the D2D CH to coordinate the D2Dchannel allocation for D2D communication within the cell. In thisscenario, a D2D UE may detect the need for D2D transmission but withoutvalid means to request UL resource allocation for sending a D2D channelallocation request (e.g., when the D2D UE is in RRC idle state or in RRCconnected state with UL synchronization status as “non-synchronized”).

FIG. 2a illustrates a flow chart of a method, according to anembodiment. The method of FIG. 2a may be carried out by a node, serveror host facilitating proximity-based services, for example for a clusterof user devices. Proximity-based services may include device-to-device(D2D) communications, proximity services (ProSe), machine typecommunications (MTC), such a cyber physical systems or Internet ofthings, etc. or any combination thereof.

As illustrated in FIG. 2a , at block 100, the method includescontrolling receiving of a request for proximity-based service on arandom access channel. The request may be for at least one resource.

According to an embodiment, a D2D UE may utilize RACH procedure torequest D2D resource allocation from a serving eNB. The D2D UE can use,for example, msg3 in RA procedure to deliver the pre-configured UE IDand optional group ID for D2D communication as a D2D channel allocationrequest. In certain embodiments, the D2D channel allocation request canbe introduced either as MAC control signaling or a RRC control message.

In the example of FIG. 2a , at block 110, it is determined whether therequested at least one resource is allocable within a random accesscontention window.

In general, in contention based random access, any device in the networkcan transmit random access preamble probably followed by datatransmission at configured time instance. The overlapping transmission(i.e. collision) of random access preamble and data may occur. In orderto resolve the collision, contention resolution message needs to beprovided to the random access device within certain time period. Acontention window defines the period of time during which the contentionresolution message is expected by the random access device aftertransmitting random access preamble or data. The contention based randomaccess configuration and contention window size may be controlled by anode supporting the service at issue.

According to an embodiment, the determination of whether the requestedat least one resource is allocable within the random access contentionwindow may be carried out by finding out at least one of the following:weather there is available D2D resources to be allocated and whether auser device requesting the at least one resource is in connected stateand/or security functions of the proximity-based service are under thecontrol of the network node. This enables quick authentication of theD2D UE and the prompt availability of D2D resources. For instance, quickauthentication may be possible if the D2D UE is in RRC connected statebefore requesting the D2D resource or D2D security server/agentfunctions are located in eNB or within the radio access network that isunder control of the eNB.

According to an embodiment, upon receiving a D2D resource request usingRACH from a D2D UE, the eNB determines if the requested D2D resource canbe allocated within RACH contention window and determines whether thereis a need for RRC connection establishment for the D2D UE. For anexample of D2D resource availability, the requested D2D resource may notbe available immediately when the eNB receives a D2D resource requestfrom the D2D UE. However, if the requesting D2D UE has higher priorityto use the resources, the eNB may coordinate the usage of D2Dresource(s) in such way that other lower priority D2D UEs or D2D groupmay be requested to release certain D2D resource(s) for the requestingD2D UE. In this case, the requested D2D resource may be allocated onlyafter low priority D2D UEs/group releases the resource as requested.

As depicted in FIG. 2a , at block 115, when it is determined that the atleast one resource is allocable, a transmission of allocationinformation on a common control channel is prepared. In one embodiment,the transmission of allocation information on a common control channelis carried out as a contention resolution of a random access procedure.In other words, if the requested D2D resource can be allocated withinRACH contention window, the eNB may transmit D2D resource allocation onthe pre-configured D2D common control channel, which can also be used ascontention resolution message towards the D2D UE requesting the D2Dresource with RACH procedure. Therefore, msg 4 of RACH procedure forcontention resolution may be skipped in this case.

Returning to FIG. 2a , when the at least one resource is not allocable,at block 120, a response for the request on the random access responsechannel is prepared, and a transmission of allocation information eitheron common control channel or dedicated control channel is prepared. Inan embodiment, if the D2D UE requesting the at least one resource is inidle state, the preparing of the response for the request on the randomaccess response channel may further comprise including a radio resourceconnection setup in the response. In one embodiment, the radio resourceconnection setup or the response for the request on the random accessresponse channel may further comprise allocation information and thenthe preparing of a transmission of allocation information either on thecommon control channel or the dedicated control channel is not carriedout.

If requested D2D resource cannot be allocated within RACH contentionwindow, the eNB may transmit RACH response message to keep the D2D UEinto RRC connected state. The D2D resource allocation may be transmittedto the D2D UE later on either on pre-configured D2D common controlchannel or with dedicated signaling.

In one embodiment, if the eNB determines that there is a need forestablishing a RRC connection for RRC idle mode D2D UE (e.g., when theeNB wants to coordinate/control D2D group communication to a certainextent and uses the RRC connected mode D2D UE to communicate thecoordination/control messages to the D2D group or some dynamic D2Dchannel allocation using dedicated RRC signaling is preferred), the eNBmay include a RRC connection setup message in a RACH response messagesent to the D2D UE, in which D2D resource allocation may or may not beincluded.

The eNB being able to allocate resources to D2D UE despite the UE'sstatus of activity (e.g., connected/idle mode) achieves certainadvantages, such as reducing radio resource consumption, complexity andsignaling overhead (which are otherwise needed in order to establish andmaintain active UE contexts and mobility connections for UEs). This inturn improves radio network capacity and energy efficiency.

FIG. 2b illustrates a flow chart of a method, according to anotherembodiment. In one embodiment, the method of FIG. 2b may be carried outby a user device for proximity-based services. Proximity-based servicesmay include device-to-device (D2D) communications, proximity services(ProSe), machine type communications (MTC), such as cyber physicalsystems or Internet of things, etc. or any combination thereof.

As illustrated in FIG. 2b , at block 130, the method may includedetermining a need for at least one resource for proximity-basedservice. The determination may be based, for example, on a need totransmit a video clip or an e-mail.

At block 135, transmission of a resource request on a random accesschannel for the at least one resource is controlled.

According to an embodiment, a D2D UE may utilize RACH procedure torequest D2D resource allocation from a serving eNB. The D2D UE can use,for example, msg3 in RA procedure to deliver the pre-configured UE IDand optional group ID for D2D communication as a D2D channel allocationrequest. In certain embodiments, the D2D channel allocation request canbe introduced either as MAC control signaling or a RRC control message.

At block 140, feedback in response to the resource request is monitored.Both a common control channel and random access response channel may bemonitored.

In an embodiment, upon transmitting a D2D resource request, the D2D UEmay need to monitor feedback from eNB for possible D2D resourceallocation and/or RACH response within RACH contention window. Forexample, the D2D UE may monitor both PDCCH for scheduling information ofmsg4 as RACH response and the update of D2D common control channel forD2D channel allocation response.

At block 145, a current activity status is maintained, when resourceallocation for the proximity-based service is obtained on a commoncontrol channel. The maintaining of the status may be based on regardingresource allocation on the common control channel as a contentionresolution. Thus, the user device does not have to monitor a separatecontention resolution message (msg4) from random access responsechannel.

In one embodiment, if D2D resource allocation is received from the eNBon the pre-configured D2D common control channel, the D2D UE considersit succeeded in contention based RACH procedure and can remain in thesame RRC state as it was before initiating RACH procedure. In this case,the D2D UE can start the transmission for D2D broadcast/groupcommunication on allocated D2D channel(s) based on D2D channelallocation information provided by updated D2D common control channel.

As illustrated in FIG. 2b , at block 150, when a response to theresource request is obtained on a random access response channel, theD2D UE remains in a connected state for obtaining resource allocationfor the proximity-based service.

In one embodiment, if a RACH response, either with or without D2Dresource allocation, is received from the eNB, the D2D UE stays in RRCconnected state for further communication with the eNB. If the D2D UEwas in RRC idle state before initiating RACH procedure, the D2D UE mayneed to establish RRC connection with the eNB as commanded in RACHresponse message. If D2D resource allocation is not included in RACHresponse message, the D2D UE may get D2D resource allocation latereither on pre-configured D2D common control channel or on the dedicatedcontrol channel, which may happen out of RACH contention window.

Referring again to FIG. 2b , at block 155, retransmission of theresource request on a random access channel after a back-off period oftime is controlled, when a response to the resource request is notobtained.

If nothing is received within RACH contention window, the D2D UE mayreattempt sending the D2D resource request utilizing RACH procedureafter a back-off time period. The back-off time period may be set by acontrolling node.

A benefit of allowing D2D UE to remain in current state (especiallyidle) while receiving D2D allocation are to reduce radio resourceconsumption, complexity and signaling overhead (which are otherwiseneeded in order to establish and maintain active UE contexts andmobility connections for UEs). This in turn improves radio networkcapacity and energy efficiency.

FIG. 3 illustrates an example signaling diagram of a RA procedure basedD2D channel allocation with eNB, according to one embodiment. In thisexample, the eNB acts as the D2D CH to coordinate the D2D channelallocation for D2D communication within the cell. When D2D UE detects,at 200, the need for D2D transmission but without valid means to requestUL resource allocation for sending D2D Channel Allocation Request (e.g.,when D2D UE in RRC idle state or in RRC connected state with ULsynchronization status as “non-synchronized”), a RA procedure will beinitiated. The normal RA Preamble (Msg1) and RA Response (Msg2) ascurrently specified in LTE may be used in this case. However, if D2Dchannel allocation as the cause of RA is beneficial to be indicated tothe eNB, some specific RA preambles or preamble group may bepre-configured for D2D UEs to request D2D channel allocation.

In the example of FIG. 3, the D2D UE uses msg3 in RA procedure todeliver the pre-configured UE ID and optional group ID for D2Dcommunication as a D2D channel allocation request. Upon receiving msg3,at 205, the eNB may determine the content of msg4. In order to allowun-successful D2D UE in contention to try again within a certain timelimit, msg4 of contention resolution may be sent before the eNBauthenticates the D2D UE with the D2D security server/agent (SeA) at210. If the requested D2D UE is authenticated by the SeA and the eNB hasavailable D2D channels resource to allocate, the eNB may, at 215, updatethe D2D broadcast channel to confirm the channel allocation. The updatedchannel allocation information may be used by the requested D2D UE asthe response of D2D channel allocation and by corresponding D2D groupmember to monitor, at 220, the allocated D2D channel(s) for receivingD2D communication packets. It may also be used by the requested D2D UEas contention resolution if msg4 is skipped by eNB. At 225, the D2D UEmay start D2D transmission on the allocated D2D channel(s).

It is noted that at least some embodiments may be applied for the casehaving eNB with broken S1 to assist D2D communications.

The steps/points, signaling messages and related functions describedabove in FIGS. 2a, 2b , and 3 are in no absolute chronological order,and some of the steps/points may be performed simultaneously or in anorder differing from the given one. Other functions may also be executedbetween the steps/points or within the steps/points and other signalingmessages sent between the illustrated messages. Some of the steps/pointsor part of the steps/points can also be left out or replaced by acorresponding step/point or part of the step/point.

FIG. 4a illustrates an example of an apparatus 10 according to anembodiment. In an embodiment, apparatus 10 may be a node, host, server,and/or base station in a communications network or serving such anetwork, such as an evolved node B (eNB) in LTE or LTE-A. It should benoted that one of ordinary skill in the art would understand thatapparatus 10 may include components or features not shown in FIG. 4 a.

As illustrated in FIG. 4a , apparatus 10 may include a processor 22 forprocessing information and executing instructions or operations.Processor 22 may be any type of general or specific purpose processor.While a single processor 22 is shown in FIG. 4a , multiple processorsmay be utilized according to other embodiments. In fact, processor 22may include one or more of general-purpose computers, special purposecomputers, microprocessors, digital signal processors (DSPs),field-programmable gate arrays (FPGAs), application-specific integratedcircuits (ASICs), and processors based on a multi-core processorarchitecture, as examples.

Apparatus 10 may further comprise or be coupled to a memory 14 (internalor external), which may be coupled to processor 22, for storinginformation and/or instructions that may be executed by processor 22.Memory 14 may be one or more memories and of any type suitable to thelocal application environment, and may be implemented using any suitablevolatile or nonvolatile data storage technology such as asemiconductor-based memory device, a magnetic memory device and system,an optical memory device and system, fixed memory, and removable memory.For example, memory 14 may be comprised of any combination of randomaccess memory (RAM), read only memory (ROM), static storage such as amagnetic or optical disk, or any other type of non-transitory machine orcomputer readable media. Instructions (which may be stored in memory 14)may include program instructions or computer program code or computerprogram code portions that, when executed by processor 22, for example,enable the apparatus 10 to perform tasks as described herein. Thecomputer program may be in source code form, object code form, or insome intermediate form, and it may be stored in some sort of carrier,distribution medium, or computer readable medium, which may be anyentity or device capable of carrying the program. Such carriers includea record medium, computer memory, read-only memory, photoelectricaland/or electrical carrier signal, telecommunications signal, andsoftware distribution package, for example. Depending on the processingpower needed, the computer program may be executed in a singleelectronic digital computer or it may be distributed amongst a number ofcomputers. The computer readable medium or computer readable storagemedium may be a non-transitory medium.

Apparatus 10 may also comprise or be coupled to one or more antennas 25for transmitting and receiving signals and/or data to and from apparatus10. Apparatus 10 may further comprise or be coupled to a transceiver 28configured to transmit and receive information. The transceiver may bean external device, such as a remote radio head. For instance,transceiver 28 may be configured to modulate information on to a carrierwaveform for transmission by the antenna(s) 25 and demodulateinformation received via the antenna(s) 25 for further processing byother elements of apparatus 10. In other embodiments, transceiver 28 maybe capable of transmitting and receiving signals or data directly.

Processor 22 may perform functions associated with the operation ofapparatus 10 including, without limitation, precoding of antennagain/phase parameters, encoding and decoding of individual bits forminga communication message, formatting of information, and overall controlof the apparatus 10, including processes related to management ofcommunication resources.

In an embodiment, memory 14 stores software modules that providefunctionality when executed by processor 22. The modules may include,for example, an operating system that provides operating systemfunctionality for apparatus 10. The memory may also store one or morefunctional modules, such as an application or program, to provideadditional functionality for apparatus 10. The components of apparatus10 may be implemented in hardware, or as any suitable combination ofhardware and software.

As mentioned above, according to one embodiment, apparatus 10 may be aserver, network node, host or base station in a communications networkor serving such a network. In this example embodiment, apparatus 10 maybe an eNB as discussed above. In one embodiment, apparatus 10 may becontrolled by memory 14 and processor 22 to receive a D2D resourcerequest using RACH from a D2D UE. According to an embodiment, the D2Dresource request may be received in msg3 of random access (RA)procedure. Apparatus 10 may then be controlled by memory 14 andprocessor 22 to determine if the D2D resource can be allocated withinthe RACH contention window. In one embodiment, if the D2D resource canbe allocated within RACH contention window, apparatus 10 may becontrolled by memory 14 and processor 22 to prepare a transmission ofallocation information using a common control channel.

According to certain embodiments, if the D2D resource cannot beallocated within RACH contention window, apparatus 10 may be controlledby memory 14 and processor 22 to prepare a RACH response (for enablingUE to stay in connected mode) and prepare a transmission of allocationinformation using either a common control channel or dedicated controlchannel.

According to an embodiment, when apparatus 10 determines that a RRCconnection for D2D UE should be established, apparatus 10 may becontrolled by memory 14 and processor 22 to include a RRC connectionsetup message in RACH response message to D2D UE, in which D2D resourceallocation may or may not be included.

In certain embodiments, apparatus 10 may be controlled by memory 14 andprocessor 22 to contact a security server to authenticate the D2D UE,and to receive a D2D group security context comprising authenticationinformation for each individual group member by the security server ifno security risk is identified. In one embodiment, the security servermay be a D2D security server/agent (SeA).

FIG. 4b illustrates an example of an apparatus 20 according to anembodiment. In an embodiment, apparatus 20 may be a device or node in acommunications network, such as a user device (which may also be calledUE, user equipment, user terminal, terminal device, etc.). The userdevice typically refers to a portable computing device that includeswireless mobile communication devices operating with or without asubscriber identification module (SIM), including, but not limited to,the following types of devices: a mobile station (mobile phone),smartphone, personal digital assistant (PDA), handset, device using awireless modem (alarm or measurement device, etc.), laptop and/or touchscreen computer, tablet, phablet, game console, notebook, and multimediadevice. It should be appreciated that a user device may also be a nearlyexclusive uplink only device, of which an example is a camera or videocamera loading images or video clips to a network.

It should be noted that one of ordinary skill in the art wouldunderstand that apparatus 20 may include components or features notshown in FIG. 4 b.

As illustrated in FIG. 4b , apparatus 20 may include a processor 32 forprocessing information and executing instructions or operations.Processor 32 may be any type of general or specific purpose processor.While a single processor 32 is shown in FIG. 4b , multiple processorsmay be utilized according to other embodiments. In fact, processor 32may include one or more of general-purpose computers, special purposecomputers, microprocessors, digital signal processors (DSPs),field-programmable gate arrays (FPGAs), application-specific integratedcircuits (ASICs), and processors based on a multi-core processorarchitecture, as examples.

Apparatus 20 may further comprise or be coupled to a memory 34 (internalor external), which may be coupled to processor 32, for storinginformation and instructions that may be executed by processor 32.Memory 34 may be one or more memories and of any type suitable to thelocal application environment, and may be implemented using any suitablevolatile or nonvolatile data storage technology such as asemiconductor-based memory device, a magnetic memory device and system,an optical memory device and system, fixed memory, and removable memory.For example, memory 34 may be comprised of any combination of randomaccess memory (RAM), read only memory (ROM), static storage such as amagnetic or optical disk, or any other type of non-transitory machine orcomputer readable media. Instructions (which may be stored in memory 34)may include program instructions or computer program code or computerprogram code portions that, when executed by processor 32, enable theapparatus 20 to perform tasks as described herein. The computer programmay be in source code form, object code form, or in some intermediateform, and it may be stored in some sort of carrier, distribution medium,or computer readable medium, which may be any entity or device capableof carrying the program. Such carriers include a record medium, computermemory, read-only memory, photoelectrical and/or electrical carriersignal, telecommunications signal, and software distribution package,for example. Depending on the processing power needed, the computerprogram may be executed in a single electronic digital computer or itmay be distributed amongst a number of computers. The computer readablemedium or computer readable storage medium may be a non-transitorymedium.

Apparatus 20 may also comprise or be coupled to one or more antennas 35for transmitting and receiving signals and/or data to and from apparatus20. Apparatus 20 may further comprise or be coupled to a transceiver 38configured to transmit and receive information. The transceiver may bean external device, such as a remote radio head. For instance,transceiver 38 may be configured to modulate information on to a carrierwaveform for transmission by the antenna(s) 35 and demodulateinformation received via the antenna(s) 35 for further processing byother elements of apparatus 20. In other embodiments, transceiver 38 maybe capable of transmitting and receiving signals or data directly.

Processor 32 may perform functions associated with the operation ofapparatus 20 including, without limitation, precoding of antennagain/phase parameters, encoding and decoding of individual bits forminga communication message, formatting of information, and overall controlof the apparatus 20, including processes related to management ofcommunication resources.

In an embodiment, memory 34 stores software modules that providefunctionality when executed by processor 32. The modules may include,for example, an operating system that provides operating systemfunctionality for apparatus 20. The memory may also store one or morefunctional modules, such as an application or program, to provideadditional functionality for apparatus 20. The components of apparatus20 may be implemented in hardware, or as any suitable combination ofhardware and software.

As mentioned above, according to one embodiment, apparatus 20 may be adevice or node in a communications network. In this example embodiment,apparatus 20 may be a user device. In one embodiment, apparatus 20 maybe controlled by memory 34 and processor 32 to determine the need for aD2D resource, and to transmit a D2D resource request utilizing RACHprocedure to an eNB. In one embodiment, the resource request may beincluded in msg3 in RA procedure and/or in a D2D channel allocationrequest. In an embodiment, the resource request may comprise a D2D UEidentity and/or a group identity.

According to one embodiment, memory 34 and processor 32 may controlapparatus 20 to monitor feedback from the eNB in response to the D2Dresource request. If D2D resource allocation is received from the eNB ona D2D common control channel, memory 34 and processor 32 may controlapparatus 20 to maintain its activity status (e.g., connected or idle).In an embodiment, if apparatus 20 receives a RACH response either withor without resource allocation, apparatus 20 may be controlled by memory34 and processor 32 to remain in connected state with the eNB forfurther communication. According to one embodiment, if no allocation isreceived, apparatus 20 may be controlled by memory 34 and processor 32to reattempt sending the D2D resource request utilizing RACH procedureafter a back-off time period.

In one embodiment, when the eNB determines that RRC connection should beestablished for apparatus 20, apparatus 20 may be controlled by memory34 and processor 32 to receive a RRC connection setup message to triggerapparatus 20 to establish RRC connection with the eNB. Accordingly, inthis embodiment, apparatus 20 may be controlled by memory 34 andprocessor 32 to establish the RRC connection with the eNB according tothe RRC connection setup message.

According to certain embodiments, apparatus 20 may be controlled bymemory 34 and processor 32 to start transmission for D2D broadcastcommunication on the D2D channel allocation and configuration receivedfrom the eNB. In an embodiment, apparatus 20 may be further controlledby memory 34 and processor 32 to receive an activation time instanceindicating an earliest starting time the allocated D2D channel may betaken into use for the transmission.

FIG. 5a illustrates an exemplifying block diagram of an apparatus 500according to another embodiment. It should be understood that anapparatus may also be similar to the apparatus of FIG. 4a or it may aprocessor, control unit or alike.

Apparatus 500 may include means 502 (22) for controlling receiving arequest for proximity-based service on a random access channel. Therequest may be for at least one resource. Apparatus 500 (22) may alsoinclude means 505 (22) for determining whether the requested at leastone resource is allocable within a random access contention window.Apparatus 500 may further include means 510 (22) for preparing atransmission of allocation information on a common control channel, whenit is determined that the at least one resource is allocable. Apparatus500 may include means 515 (22) for preparing a response for the requeston the random access response channel and for preparing a transmissionof allocation information either on a common control channel ordedicated control channel, when it is determined that the at least oneresource is not allocable.

FIG. 5b illustrates an exemplifying block diagram of an apparatus 501,according to another embodiment. It should be understood that anapparatus may also be similar to the apparatus of FIG. 4b or it may aprocessor, control unit or alike.

Apparatus 501 may include means 520 (32) for determining a need for atleast one resource for proximity-based service. Apparatus 501 mayfurther include means 525 (32) for controlling transmission of aresource request on a random access channel for the at least oneresource. According to one embodiment, apparatus 501 may also includemeans 530 (32) for monitoring feedback in response to the resourcerequest. Apparatus 501 may include means 535 (32) for maintaining acurrent activity status, when resource allocation for theproximity-based service is obtained on a common control channel.Apparatus 501 may include means 540 (32) for remaining in a connectedstate for obtaining resource allocation for the proximity-based service,when a response to the resource request is obtained on a random accessresponse channel. Apparatus 501 may include means 545 (32) forcontrolling retransmission of the resource request on a random accesschannel after a back-off time period, when a response to the resourcerequest is not obtained.

It should be appreciated that an apparatus may include or otherwise bein communication with a control unit, one or more processors or otherentities capable of carrying out operations according to the embodimentsdescribed by means of FIGS. 2a and 2 b. It should be understood thateach block of the flowchart of FIG. 2a or 2 b and any combinationthereof may be implemented by various means or their combinations, suchas hardware, software, firmware, one or more processors and/orcircuitry.

In some embodiments, the functionality of any of the methods describedherein, such as that illustrated in FIG. 2a, 2b , or 3 discussed above,may be implemented by software and/or computer program code or computerprogram code portions stored in memory or other computer readable ortangible media, and executed by a processor. In other embodiments, thefunctionality may be performed by hardware or combination of softwareand hardware, for example through the use of an application specificintegrated circuit (ASIC), a programmable gate array (PGA), a fieldprogrammable gate array (FPGA), etc.

One having ordinary skill in the art will readily understand that theinvention as discussed above may be practiced with steps in a differentorder, and/or with hardware elements in configurations which aredifferent than those which are disclosed. Therefore, although theinvention has been described based upon these preferred embodiments, itwould be apparent to those of skill in the art that certainmodifications, variations, and alternative constructions would beapparent, while remaining within the spirit and scope of the invention.In order to determine the metes and bounds of the invention, therefore,reference should be made to the appended claims.

We claim:
 1. A method, comprising: controlling receiving, by a networknode, a request for proximity-based service on a random access channel,the request being for at least one resource; determining whether therequested at least one resource is allocable within a random accesscontention window; when the at least one resource is allocable,preparing a transmission of allocation information on a common controlchannel, when the at least one resource is not allocable, preparing aresponse for the request on the random access response channel, andpreparing a transmission of allocation information either on commoncontrol channel or dedicated control channel.
 2. The method according toclaim 1, wherein the determining comprises determining at least one ofthe following: whether a user device requesting the at least oneresource is in connected state and security functions of theproximity-based service are under the control of the network node. 3.The method according to claim 1, wherein the preparing of thetransmission of allocation information on the common control channel iscarried out as a contention resolution of a random access procedure. 4.The method according to claim 1, wherein the request for proximity-basedservice is received in msg3 of random access (RA) procedure.
 5. Themethod according to claim 1, wherein, if a user device requesting the atleast one resource is in idle state, the preparing of the response forthe request on the random access response channel further comprisesincluding a radio resource connection setup into the response.
 6. Themethod according to claim 1, wherein the radio resource connection setupor the response for the request on the random access response channelfurther comprises allocation information and the preparing atransmission of allocation information either on common control channelor dedicated control channel is not carried out.
 7. An apparatus,comprising: at least one processor; and at least one memory includingcomputer program code, wherein the at least one memory and the computerprogram code are configured, with the at least one processor, to causethe apparatus at least to control receiving a request forproximity-based service on a random access channel, the request beingfor at least one resource; determine whether the requested at least oneresource is allocable within a random access contention window; when theat least one resource is allocable, prepare a transmission of allocationinformation on a common control channel, when the at least one resourceis not allocable, prepare a response for the request on the randomaccess response channel, and prepare a transmission of allocationinformation either on common control channel or dedicated controlchannel.
 8. The apparatus according to claim 7, wherein the at least onememory and the computer program code are further configured, with the atleast one processor, to cause the apparatus at least to determine atleast one of the following: whether a user device requesting the atleast one resource is in connected state and security functions of theproximity-based service are under the control of the network node. 9.The apparatus according to claim 7, wherein the preparing of thetransmission of allocation information on the common control channel iscarried out as a contention resolution of a random access procedure. 10.The apparatus according to claim 7, wherein the request forproximity-based service is received in msg3 of random access (RA)procedure.
 11. The apparatus according to claim 7, wherein, if a userdevice requesting the at least one resource is in idle state, the atleast one memory and the computer program code are further configured,with the at least one processor, to cause the apparatus at least toprepare the response for the request on the random access responsechannel by including a radio resource connection setup into theresponse.
 12. The apparatus according to claim 7, wherein the radioresource connection setup or the response for the request on the randomaccess response channel further comprises allocation information and thepreparing a transmission of allocation information either on commoncontrol channel or dedicated control channel is not carried out.
 13. Amethod, comprising: determining, by a device, a need for at least oneresource for proximity-based service; controlling transmission of aresource request on a random access channel for the at least oneresource, wherein the resource request is transmitted in msg3 in randomaccess (RA) procedure, wherein the resource request comprises at leastone of the following: a user identity or group identity; monitoringfeedback in response to the resource request, wherein the monitoringcomprises monitoring both the common control channel and random accessresponse channel; when resource allocation for the proximity-basedservice is obtained on a common control channel, maintaining a currentactivity status, wherein the current activity status comprises one of:connected or idle; when a response to the resource request is obtainedon a random access response channel, remaining in a connected state forobtaining resource allocation for the proximity-based service; when aresponse to the resource request is not obtained, controllingretransmission of the resource request on a random access channel aftera back-off period of time.
 14. The method according to claim 13, whereinthe maintaining of the current activity status is based on regardingresource allocation on the common control channel as a contentionresolution.
 15. An apparatus, comprising: at least one processor; and atleast one memory including computer program code, wherein the at leastone memory and the computer program code are configured, with the atleast one processor, to cause the apparatus at least to determine a needfor at least one resource for proximity-based service; controltransmission of a resource request on a random access channel for the atleast one resource, wherein the resource request is transmitted in msg3in random access (RA) procedure, wherein the resource request comprisesat least one of the following: a user identity or group identity;monitor feedback in response to the resource request; wherein themonitoring comprises monitoring both the common control channel andrandom access response channel, when resource allocation for theproximity-based service is obtained on a common control channel,maintain a current activity status, wherein the current activity statuscomprises one of: connected or idle; when a response to the resourcerequest is obtained on a random access response channel, remain in aconnected state for obtaining resource allocation for theproximity-based service; when a response to the resource request is notobtained, control retransmission of the resource request on a randomaccess channel after a back-off period of time.
 16. The apparatusaccording to claim 15, wherein apparatus comprises a D2D user device.17. The apparatus according to claim 15, wherein the maintaining of thecurrent activity status is based on regarding resource allocation on thecommon control channel as a contention resolution.